There is substantial evidence that the central nervous system of young children is marked by "plasticity" or the ability to make compensatory changes in its functional architecture. For example, children may redevelop the ability to speak or to walk after damage to the speech or motor areas. Adults are much less likely to respond in this way. Similar phenomena have been studies in animal experiments where it has been possible to crate detailed cortical maps showing which parts of the remaining brain tissue assume the functions of damaged areas. In the last few years, magnetic resonance imaging (MRI) techniques have been developed to detect signals in functionally active parts of the brain. With appropriate computer graphic and image processing techniques, functional MRI (FMRI) signals can be combined with conventional MR images to create integrated 3-D models of cortical structure and function of individual subjects. However, these computational methods need to be automated so that it is practical to apply them to the huge volumes of data produced by fast MRI acquisitions. Our long-term goal is to develop practical computational tools and MRI technology for the creation of 3-D maps of cortical structure and function. We will use this technology to study the functional reorganization of brains of young adults who sustained anatomical brain damage at an early age. Theoretically, such experiments would increase our understanding of the spatial, temporal, and functional limits of human brain plasticity. Practically, this type of information could help neurosurgeons plan the resection of brain lesions so that important functional areas are left intact. The project will be divided into three parts: 1. Image Segmentation Methods. Software will be developed for automatic identification of the brain surface in MR head images. By greatly reducing the labor required to perform this type of image segmentation, this software will promote the routine use of MRI-derived 3-D brain models for many purposes, including neurosurgical planning and multimodality display. 2. Intraoperative Validation of FMRI. It is important to characterize the accuracy of FMRI as a brain-mapping tool. To do this, FMRI will be sued to predict the location of the sensorimotor cortex in patients scheduled to undergo resection of a small brain tumor. Stereotactic surgical methods will be used to compare the FMRI prediction with the location of the sensorimotor cortex determined by electrocorticography. 3. Brain Mapping of Hemiplegic Subjects. FMRI data and image processing will be used to create cortical maps of bilateral sensorimotor areas in normal volunteers and in age-matched hemiplegic subjects with neonatal brain damage. The spatial distribution of functional activity in these tow groups will be compared with the aid of these cortical maps and also by using a common reference frame, derived from a stereotactic brain atlas. Since the FMRI data from all subjects will be mapped into an atlas-defined reference frame, these data can be readily utilized by other investigators.